1. Field of the Invention
The present invention relates generally to photovoltaic devices, and more particularly to patterned glass for use in photovoltaic cells that is capable of concentrating solar energy.
2. Discussion of the Background
All United States Patents and Patent Applications referred to herein are hereby incorporated by reference in their entireties. In the case of conflict, the present specification, including definitions, will control.
As the global population continues to grow, so does the demand for energy and energy sources. Fossil fuel consumption has seen steady increases during the last century, as expected for an energy thirsty global population. It was estimated that in 2004, 86% of human-produced energy came from the burning of fossil fuels. Fossil fuels are non-renewable resources and fossil fuel reserves are being depleted quicker than they can be replaced. As a result, a movement toward the development of renewable energy has been undertaken to meet increased demand for energy. Over the last ten to twenty years, there has been an increased focus on developing technology to efficiently harness energy from alternative sources, such as solar, hydrogen and wind energy to meet the increased global demand.
Of the alternative sources, the sun is considered the most abundant natural resource, with an infinite supply of energy showering the Earth on a daily basis. Numerous technologies exist that are directed to capturing the sun's light energy and converting it into electricity. A photovoltaic (PV) module represents such a technology and, to date, has found many applications in areas such as remote power systems, space vehicles and consumer products such as wireless devices.
Energy from the sun, while vast and abundant, is actually quite diffuse. For example, the generation of about a gigawatt of power using modern PV systems would require an area of approximately four square miles of silicon. The use of such large amounts of silicon is the biggest cost factor imparted to PV device manufacturers, who, in turn, pass along the cost to customers who wish to purchase and utilize such PV devices. To date, electricity generated from PV systems is more expensive than electricity generated from the traditional burning of fossil fuels, thus, hindering electricity generated from PV systems from being economically competitive with electricity generated from fossil fuels.
One avenue that is being taken to reduce the cost of generating electricity from PV systems is to use less PV material, such as silicon, in the PV device. By using less PV material, naturally, there is less space, or surface area, potentially available for being hit by the sun's energy. To be able to practically utilize PV systems that possess less silicon material without a significant drop-off in PV device conversion efficiency, solar concentrators have been used as a means to focus the sun's energy onto a smaller area of silicon.
The idea of solar concentration to reduce the size of PV systems has been around for decades, but has only taken off recently with the advancement in the efficiency of PV devices. There exists a number of different optical components that can be used to concentrate solar energy, including curved mirrors, patterned plastic sheets, curved metal reflectors and special lenses, such as Fresnel lenses. Incorporation of these optical components has given rise to a class of PV systems known as “concentrator” PV devices.
The fabrication of “concentrator” PV devices offers advantages over flat plate, or non-concentrator, PV devices. These advantages can include, but are not limited to: 1) concentrator PV devices can increase power output while simultaneously reducing the number of solar cells needed; and 2) concentrator PV devices can utilize solar cells that are of a much smaller surface area, which are easier to mass-produce as compared to large surface area solar cells. While offering the aforementioned advantages, the optical components themselves (e.g., curved mirrors, patterned plastic sheets, curved metal reflectors or special lenses) can be quite expensive, thereby somewhat off-setting the reduced costs associated with using less PV material in a concentrator PV device. Moreover, these optical components vary in terms of the increase in energy output they provide for the PV device (as compared with non-concentrator PV devices) and increased costs. For example, one such PV device, produced by Solaria, utilizes a plastic V-groove patterned sheet in a PV device. The plastic patterned sheet is flat on one optical surface and has a series of adjacently disposed triangular (i.e., V-groove) patterns disposed on the other optical surface. The PV device includes solar cell material with the patterned plastic sheet disposed on the solar cell material (with V-groove pattern directed towards the solar cell material) and requires the use of cover glass disposed on top of the plastic sheet. While more energy efficient than non-concentrator PV devices, the PV device suffers from the drawback that the production of the patterned plastic sheet is expensive, thereby off-setting the reduced costs associated with having less solar cell material. Moreover, the plastic sheet requires the use of cover glass, which adds to the costs, and the increase in energy output is limited
Thus, there remains a need in the art for a concentrator PV device that incorporates an optical component that can be easily and inexpensively produced, that maximizes cost savings and provides increased energy output of the PV device.